Lisp: Testing Symbol Equalities

indienick · 08-12-2007, 07:54 PM

I want to pass a symbol as an argument to a function, but the problem is I can't seem to find a way (none that come to mind, anyways) to test for an equality.

I'm writing a quick Lisp script to save me having to type in "wodim -eject -sao -vv dev=/dev/dvd file.0 file.1 ... file.n" all the time. I'm not trying to make this script efficient in any way shape or form (at least in the way the writing is structured - plus, I'm also using this as a good way to practice my Lisp hacking).

In the script, I want to pass a symbol to a function, dictating the burning style: SAO, DAO or TAO.

Code:

(defvar *device* "/dev/dvd")
(burn-data-dvd :files '("list" "of" "files")
               :device *device*
               :eject t
               :session-type 'sao)

In the function BURN-DATA-DVD I want to test to see what type of burning session was passed. I don't want to resort to passing strings, though.

What predicate do I use to test if SESSION-TYPE is equal to 'SAO, 'DAO or 'TAO? I've tried EQL, EQUAL, EQUALP and I know = won't work as it's reserved for numerical tests.

EDIT: I suppose I should explain, somewhat: the reason I'm not custom tailoring this script for my specific needs and hardware setup is so I can (in hopes) distribute this script.

colucix · 08-14-2007, 05:17 AM

I used

Code:

(strcmp string1 string2)

in Scheme. In Lisp you can try also

Code:

(string= string1 string2)
(string-equal string1 string2)

the latter should be case-insensitive! Not tested anyway...

indienick · 08-14-2007, 09:05 AM

That works perfectly, thank you very much!

I wouldn't have thought to use string-based predicates!